Merge pull request #14 from chirino/KT-1530

For KT-1530

libraries/stdlib/src/Preconditions.kt

@@ -0,0 +1,48 @@
+package kotlin
+
+object Assertions {
+    // TODO make private once KT-1528 is fixed.
+    val _ENABLED = (javaClass<java.lang.System>()).desiredAssertionStatus()
+}
+
+/**
+ * Throws an [[AssertionError]] if the `value` is false and runtime assertions have been
+ * enabled on the JVM using the `-ea` JVM option.
+ */
+inline fun assert(value:Boolean):Unit {
+    if(Assertions._ENABLED) {
+        if(!value) {
+            throw AssertionError();
+        }
+    }
+}
+
+/**
+* Throws an [[AssertionError]] with specified `message` if the `value` is false
+* and runtime assertions have been enabled on the JVM using the `-ea` JVM option.
+*/
+inline fun assert<T>(value:Boolean, message:T) {
+    if(Assertions._ENABLED) {
+        if(!value) {
+            throw AssertionError(message);
+        }
+    }
+}
+
+/**
+ * Throws an [[IllegalArgumentException]] if the `value` is false.
+ */
+inline fun require(value:Boolean):Unit {
+    if(!value) {
+        throw IllegalArgumentException();
+    }
+}
+
+/**
+* Throws an [[IllegalArgumentException]] with specified `message` if the `value` is false.
+*/
+inline fun require<T>(value:Boolean, message:T) {
+    if(!value) {
+        throw IllegalArgumentException(message.toString());
+    }
+}